Study of a-Si : H emitters for efficient carrier injection in GaAs bipolardevices

Experimental and theoretical results are presented concerning the applicati on of a wide gap amorphous silicon layer to improve the injection efficienc y into GaAs regions. A 30 nm a-Si:H film is grown by low temperature (T = 2 70 degrees C) plasma enhanced chemical vapour deposition and has an energy gap of 1.8 eV, which is 0.4 eV larger than that of the underlying crystalli ne GaAs. The pin diode which is fabricated has device quality rectifying pr operties and a reverse breakdown voltage of 120 V. When operated as a curre nt switch it has a reverse recovery time of 20-30 ns, largely determined by the minority carrier recombination in the GaAs intrinsic layer. The theore tical analysis of the device, based on a numerical physical simulator, show s that the density of states at the interface affects the forward bias volt ages and currents. (C) 2000 Elsevier Science B.V. All rights reserved.